Twist-drill.



1 No. 824,346. PATENTED JUNE 26, 1906.

P. W. PAWGETT.

TWIST DRILL.

APPLICATION FILED MAY 2,1905.

'FIG. I.

E7" Z0775. khl w W n0- Mag UNITED STATES PATENT OFFICE.

TWIST-DRILL.

Specification of Letters Patent.

Patented June 26, 1906.

Application filed May 2, 1905. Serial No. 258,530.

To all whom it may concern.-

Be it known that I, PERCY WILLIAM FAW- CETT, a subject of the King ofGreat Britain and Ireland, and a resident of Middlewood Hall, nearSheffield, county of York, England, have invented a certain new anduseful Improvement in Twist-Drills, (for which I have applied for apatent in Great Britain, No. 11,781, dated May 24, 1904,) of which thefollowing is a specification.

This invention, entitled Improvements in twist-drills, relates moreparticularly to the construction of the shank portion of such drills,which are sometimes parallel, but are usually made tapering to fit intoholes of corresponding configuration either in chucks or other likeholders for such tools, such drills when in use being carried round byfrictional contact between the shank and the holder,

and it is therefore most important that the shanks of the drill shouldfit the holder accurately, and especially so at the o posite ends.

My invention is only applicable to twistdrills having such taperedshanks, and the chief objects I have in View are to obtain more perfectcontact between the surfaces of the drill-shank and the holder; to avoidany rocking movement of the drill in the socket, and to reduce the areaupon the shank, which requires the careful process of surface-grind-111g.

The annexed drawings illustrate my said improvements.

Figure 1 is a front elevation, and Fig. 2

side view, of the shank portion of a twistdrill.

In carrying out my invention instead of making the shank A of the drillD of one continuous taper from end to end, I make the central portion B,which, for example, may be one-third, or thereabout, of its entirelength, of reduced diameter, or, if desired, there may be more than onereduced part, the amount of hardened surface requiring to be carefullyand accurately ground to size and to the correct angle, being therebyconsiderablyreduced. Also at the point of junction between the shank Aand the body D of the drill I form an annular concave groove C toprovide a clearance space between the line of the face of chuck or otherdrillholder and the drill, with the object of avoiding a right-anglejunction or corner, and there fore preventing any tendency for the drillto snap at that point from side strain or the like.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent, is

A twist-drill with tapering shank, having the central portion of theshank reduced in diameter, as hereinbefore described and shown.

In witness whereof I have hereunto set my hand in presence of twowitnesses.

PERCY WILLIAM FAWOETT.

Witnesses:

ROBERT F. DRURY, BERNARD E. DRURY.

